In some Arlington Public Schools, students eat lunch as early as 10:45 a.m., while others must wait until 1:30 p.m. The staggered lunch schedule is one adjustment the suburban Virginia school system has devised to contend with overcrowding.

Growing enrollment across many Northern Virginia schools has spurred the opening of new buildings, sparked clashes over redrawing school boundaries and forced students into classroom trailers. In Arlington, where the elementary-school-age population is rapidly growing, school system officials are facing difficult and complex planning decisions.

An elementary school is expected to open in fall 2021 and will require new boundaries, a process destined to provoke passionate responses from families. But before starting that, school system officials announced plans last week that are causing consternation among parents — Arlington wants to relocate several campuses to other buildings, which could mean that more than 2,400 students will be reassigned.

The school system, which issued two proposals Thursday, said the shifts are necessary to better balance the population at each of the schools and create more space for students in the fast-growing Rosslyn and Ballston areas.

They say the shifts are needed as Arlington’s student population surges. The school system educates more than 28,000 students — 7,780 more than a decade ago, according to enrollment numbers. Enrollment is expected to balloon to more than 30,000 students by 2021, and officials say at least three new elementary schools are needed over the next decade.

“We recognize that change is hard, especially when our students are involved, but we are looking for ways to keep as many students together as possible by balancing the impact of the next boundary process across all of our elementary schools,” Lisa Stengle, the system’s planning director, said in a statement to parents.

Arlington is hardly the only school system in Northern Virginia faced with challenges borne from a rapidly growing school population. The Alexandria School Board recently decided to expand the city’s only high school, an investment that is badly needed on a campus that educates nearly 4,000 students.

The school system in Fairfax County, which is among the largest in the country, has long wrestled with overcrowding — using more than 750 classroom trailers.

A final decision on the proposals in Arlington won’t be made by the county School Board until February, and the system has scheduled several opportunities for the public to share input. But some parents are worried about what the shifts could mean.

Last school year, parents at the bilingual Key Elementary School in Lyon Village fought plans to move the school, which relies on an even split between native ­English-language and Spanish-language speakers.

Parents argued that moving the immersion program would put it out of reach for many of the lower-income, Spanish-speaking families who moved into the neighborhood for its proximity to the school.

Key is an “option” campus, which means families must apply if they want their children to attend, with students admitted through a lottery. But several Key parents said they would not be willing to send their children to a farther-away school for the immersion program because of transportation and other challenges.

The proposals released last week revived worries in the Key community. Under the plans, Key would move to the building that houses Arlington Traditional School or to where Carlin Springs Elementary is located.

Those buildings house fewer students than the Key campus, raising concerns among parents that a move could shrink the immersion program or force students into classroom trailers. Alicia Rich, president of Key’s PTA, said she has been fielding texts and messages over WhatsApp from parents and staff members worried about the prospect of moving.

“This issue is so huge for us,” Rich said.

School system officials said they “urgently need” the Key building as a neighborhood school because of the lack of space for students.

“With immersion being a program, we can move it in its entirety to another location,” schools spokesman Frank Bellavia said in an email. “We can consider the pros and cons with the Key School community.”

The district would examine ways to prevent overcrowding if Key moves, including reducing the number of kindergarten ­classes, using classroom trailers or locating prekindergarten classes elsewhere. Arlington schools would explore the possibility of expanding immersion classes at other sites.

Under one proposal, Campbell Elementary would move to the building that houses Arlington Traditional School — a shift that Campbell’s PTA President Barbara Martinez fears would hurt the school’s diversity.

Campbell, another option school, is in an area with a high percentage of students who receive free and reduced-price lunch, but also draws families from wealthier parts of Arlington, Martinez said. She said she is worried that students who live in neighborhoods near Campbell would not elect to travel to the proposed building two miles away, in a less diverse part of the county.

Campbell follows an approach to education that emphasizes qualities such as collaboration, perseverance, responsibility and compassion. Outdoor learning is a major part of the curriculum, and the campus features an orchard, butterfly garden, a pond with turtles and garden beds that students help cultivate.

“It’s pretty insulting to the staff and school community,” Martinez said of the proposal to move the school. “It’s not very child-centered.”